The standard deviation is defined as the average amount by which individual data items in a data set differ from the arithmetic mean of all the data in the set.
The standard deviation is the square root of the variance. It is denoted by the symbol .
If a set of data has n values and if represents the mean of the data set, then the standard deviation is given by:
If electricity bills (in dollars) of 8 houses are 70, 82, 76, 79, 83, 85, 72, 77 and mean is 78 then find the standard deviation.
Correct Answer: C
Step 1: Representing the data in the table and compute X .P(X) and X2 . P(X)
Step 2: From the table, we get
Step 4: Variance
Step 5: Variance
Step 6: Standard deviation
Step 7: So, the standard deviation is 0.79.